It is believed that choice behavior reveals the underlying value of goods. The subjective values of stimuli can be changed through reward-based learning mechanisms as well as by modifying the description of the decision problem, but it has yet to be shown that preferences can be manipulated by perturbing intrinsic values of individual items. Here we show that the value of food items can be modulated by the concurrent presentation of an irrelevant auditory cue to which subjects must make a simple motor response (i.e., cue-approach training). Follow-up tests showed that the effects of this pairing on choice lasted at least 2 months after prolonged training. Eye-tracking during choice confirmed that cue-approach training increased attention to the cued items. Neuroimaging revealed the neural signature of a value change in the form of amplified preference-related activity in ventromedial prefrontal cortex.

Morality is a fundamental component of human cultures and has been defined as prescriptive norms regarding how people should treat one another, including concepts such as justice, fairness, and rights. Using fMRI, the current study examined the extent to which dispositions in justice sensitivity (i.e., how individuals react to experiences of injustice and unfairness) predict behavioral ratings of praise and blame and how they modulate the online neural response and functional connectivity when participants evaluate morally laden (good and bad) everyday actions. Justice sensitivity did not impact the neuro-hemodynamic response in the action-observation network but instead influenced higher-order computational nodes in the right temporoparietal junction (rTPJ), right dorsolateral and dorsomedial prefrontal cortex (rdlPFC, dmPFC) that process mental states understanding and maintain goal representations. Activity in these regions predicted praise and blame ratings. Further, the hemodynamic response in rTPJ showed a differentiation between good and bad actions 2 s before the response in rdlPFC. Evaluation of good actions was specifically associated with enhanced activity in dorsal striatum and increased the functional coupling between the rTPJ and the anterior cingulate cortex. Together, this study provides important knowledge in how individual differences in justice sensitivity impact neural computations that support psychological processes involved in moral judgment and mental-state reasoning.

The dorsal raphe nucleus (DRN) in the midbrain is a key center for serotonin (5-hydroxytryptamine; 5-HT)-expressing neurons. Serotonergic neurons in the DRN have been theorized to encode punishment by opposing the reward signaling of dopamine neurons. Here, we show that DRN neurons encode reward, but not punishment, through 5-HT and glutamate. Optogenetic stimulation of DRN Pet-1 neurons reinforces mice to explore the stimulation-coupled spatial region, shifts sucrose preference, drives optical self-stimulation, and directs sensory discrimination learning. DRN Pet-1 neurons increase their firing activity during reward tasks, and this activation can be used to rapidly change neuronal activity patterns in the cortex. Although DRN Pet-1 neurons are often associated with 5-HT, they also release glutamate, and both neurotransmitters contribute to reward signaling. These experiments demonstrate the ability of DRN neurons to organize reward behaviors and might provide insights into the underlying mechanisms of learning facilitation and anhedonia treatment.